Feature ©ISTOCKPHOTO.COM/JAE YOUNG JU Database-Assisted Spectrum Prediction in 5G Networks and Beyond: A Review and Future Challenges Marko Höyhtyä, Aarne Mämmelä, Alessandro Chiumento, Sofie Pollin, Martti Forsell, and Danijela Cabric Digital Object Identifier 10.1109/MCAS.2019.2925293 Date of publication: 13 August 2019 34 IEEE CIRCUITS AND SYSTEMS MAGAZINE 1531-636X/19©2019IEEE THIRD QUARTER 2019http://www.ISTOCKPHOTO.COM/JAE